Tool holder dampening system

ABSTRACT

A tool holder for use in a rotating spindle of a milling machine. The tool holder comprises a conically tapered shank portion for insertion into the spindle and a cutting tool mounting portion. Disposed between the shank and mounting portions is a flange portion. The flange portion includes a continuous channel formed therein which circumvents the shank portion and is adapted to accommodate a dampening member. The dampening member is compressable between the flange portion and the spindle when the tool holder is inserted into the spindle, and is adapted to eliminate harmonic resonance attributable to the use of the tool holder with a cutting tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to rotary cutting machines suchas milling machines, and more particularly to a vibration-dampenedspindle and tool holder assembly which is adapted to eliminate theharmonic resonance which typically occurs during the use of cuttingtools in high speed milling applications.

2. Description of the Prior Art

As is well known, various tool holders have been utilized in the priorart which interface with a rotating spindle of a machine such as amilling or boring machine to securely interface a cutting tool to themachine during the cutting of a work piece. A rotary cutting machinetypically includes a motor-rotated spindle to which a tool holder isattached, the tool holder being configured to accommodate a shankportion of a cutting tool which is ultimately used to cut a work piece.The attachment of the tool holder to the spindle is generallyaccomplished by providing a cavity in the spindle into which an upperend or shank portion of the tool holder is secured, as with anexternally threaded bolt which is advanced through a portion of thespindle and is threadably received into an internally threaded boreextending axially within the shank portion of the tool holder. In mostprior art tool holders, a central aperture is also formed in a lower endor mounting portion of the tool holder for receiving the shank portionof the cutting tool which is to be interfaced to the milling or othermachine via the tool holder. Subsequent to the insertion of the shankportion of the cutting tool into the central aperture of the toolholder, the shank portion of the tool holder is drawn or pulled tightlyinto the spindle by the tightening of the above-described bolt so as torigidly maintain the cutting tool within the tool holder.

Though interfacing the cutting tool to the cutting machine, prior arttool holders typically possess certain deficiencies which detract fromtheir overall utility. More particularly, while slower rotational speedsgenerally permit the cutting machine to perform adequately, high speedcutting, which is preferred, can cause substantial difficulty inproducing a satisfactory work as a result of the development ofvibratory forces that occur between the spindle and the tool holder.Specifically, at higher rotational cutting speeds, the cutting tooloften begins to chatter or vibrate such that adequate tool controlcannot be maintained and damage to the work piece, along with potentialinjury to the operator, can realistically occur. More particularly, thetransfer of the harmonic resonance into the tool holder may give rise toslight movements thereof relative to the spindle, and in extreme casesmay result in the tool holder loosening within the spindle. As will berecognized, the resonance of the tool holder relative to the spindleresults in the cut in the work piece being substantially out oftolerance.

A further deficiency with prior art tool holders is that the manner inwhich the shank portion of the cutting tool is secured within thecentral aperture of the tool holder often results in the non-concentricmounting of the cutting tool within the tool holder. Such non-concentricmounting is unacceptable in modern, high tolerance machiningapplications such as those performed on a vertical milling machinewherein minor variations in the concentricity of the cutting tool withinthe tool holder often cause catastrophic failure in the cuttingoperation.

The present invention addresses these and other deficiencies of theprior art tool holders by providing a tool holder which includes adampening member for eliminating the harmonic resonance which typicallyoccurs during the use of cutting tools in high speed millingapplications. In the tool holder constructed in accordance with thepresent invention, the non-concentric mounting of the shank portion ofthe cutting tool within the tool holder is also substantially eliminatedby the heat shrinking of the shank portion of the cutting tool withinthe tool holder. These, as well as other features and advantagesattendant to the present invention will be discussed in more detailbelow.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a toolholder for use in the rotating spindle of a milling machine. The toolholder comprises a conically tapered shank portion which is adapted tobe inserted into a complimentary recess within the spindle. In additionto the shank portion, the tool holder includes a cutting tool mountingportion which includes an aperture extending axially therein forreceiving the shank portion of a cutting tool. Formed between the shankand mounting portions is a circularly configured flange portion whichextends radially outward relative to the shank and mounting portions.Disposed within the peripheral edge of the flange portion is a generallyV-shaped slot or recess which is adapted to accommodate an automatedtool holder changer.

The tool holder of the present invention further comprises an annular,ring-like dampening member which is disposed within a complimentarygroove or channel disposed within the generally planar top surface ofthe flange portion and extending about (i.e., circumventing) the shankportion thereof. The dampening member is preferably fabricated from anelastomeric material, and is compressed between the flange portion andthe generally planar distal end of the spindle when the shank portion ofthe tool holder is inserted into and secured within the spindle. Thecomplete insertion of the tool holder into the spindle is preferablyfacilitated in a manner wherein direct, metal-to-metal contact isachieved between the distal end of the spindle and the top surface ofthe flange portion. However, such metal-to-metal contact, thoughpreferable, need not necessarily be achieved. If such metal-to-metalcontact is achieved, the abutting engagement between the distal end ofthe spindle and the top surface of the flange portion effectivelyencloses the channel within the top surface, with the dampening memberbeing sized such that, when compressed, it substantially fills theavailable open area defined by the enclosed channel and imparts aresilient biasing force against both the tool holder and the spindleseated thereagainst. When the dampening member is compressed in thismanner, it is adapted to eliminate harmonic resonance which wouldnormally otherwise occur when the shank portion of a cutting tool isinserted into the aperture of the cutting tool mounting portion of thetool holder and the cutting tool is used in a high speed millingapplication. The dampening member also creates a seal between the flangeportion of the tool holder and the spindle which prevents debris,cutting oil, or other contaminants from getting between the shankportion of the tool holder and the recess of the spindle, thusmaintaining the cleanliness of the spindle/tool holder combination. Dueto the dampening member being received into the complimentary channelformed in the top surface of the flange portion of the tool holder, thesame is prevented from excessive radial displacement when the toolholder is used in extremely high speed milling applications.

The present invention will be more apparent from the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These, as well as other features of the present invention, will becomemore apparent upon reference to the drawings wherein:

FIG. 1 is a perspective view of a tool holder constructed in accordancewith a first embodiment of the present invention as inserted into therotating spindle of a milling machine;

FIG. 2 is a partial cross-sectional view of the tool holder and spindlecombination as shown in FIG. 1;

FIG. 3 is an enlarged view of the encircled region 3 shown in FIG. 2,illustrating the dampening member of the tool holder in a compressedstate between the tool holder and the spindle of the milling machine;

FIG. 4 is a partial cross-sectional view of the tool holder of the firstembodiment similar to FIG. 3, but illustrating the dampening member ofthe tool holder in an uncompressed state resulting from the removal ofthe tool holder from within the spindle;

FIG. 5 is a partial cross-sectional view of the tool holder of the firstembodiment similar to FIG. 4, but illustrating a first potential variantin the cross-sectional configuration of the channel thereof which isused to accommodate the dampening member;

FIG. 5A is a partial cross-sectional view of the tool holder similar toFIG. 5, but depicting the dampening member in a compressed state whiledisposed within the first variant of the channel;

FIG. 6 is a partial cross-sectional view of the tool holder of the firstembodiment similar to FIGS. 4 and 5, but illustrating a second potentialvariant in the cross-sectional configuration of the channel thereofwhich is used to accommodate the dampening member;

FIG. 7 is a partial cross-sectional view of a tool holder constructed inaccordance with a second embodiment of the present invention andincluding one or more dampening members disposed within the conicalshank portion thereof;

FIG. 8 is a partial, cross-sectional view of a machine tool spindlewhich may be outfitted with one or more internal dampening members inaccordance with one aspect of the present invention;

FIG. 9 is a partial cross-sectional view of the tool holder and spindlecombination similar to FIG. 2, but further illustrating an optionalretention knob member which may be cooperatively engaged to the shankportion of the tool holder constructed in accordance with either thefirst or second embodiments of the present invention;

FIG. 10 is a partial cross-sectional view of a tool holder constructedin accordance with a third embodiment of the present invention andincluding a shrink on sleeve which defines the tapered outer surface ofthe shank portion of the tool holder; and

FIG. 11 is a top perspective view of an adapter ring constructed inaccordance with another aspect of the present invention for optional usein interfacing the tool holder of the first, second or third embodimentsto the spindle.

Common reference numerals are used throughout the drawings and thedetailed description to indicate the same elements.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes ofillustrating preferred embodiments of the present invention only, andnot for purposes of limiting the same, FIG. 1 perspectively illustratesa tool holder 10 which is constructed in accordance with the presentinvention and adapted for use in the rotating spindle 12 of a machinesuch as a milling machine or a boring machine. The tool holder 10comprises a conically tapered shank portion 14 which is adapted to beinserted into a complimentary recess 16 within the spindle 12. In thisregard, in the tool holder 10, the slope of the tapered inner surface 17of the recess 16 corresponds to the slope of the tapered outer surface15 of the shank portion 14, with the shank portion 14 being firmlyseated with the recess 16 when the tool holder 10 is properly secured tothe spindle 12. More particularly, in tool holder and spindlecombinations known in the prior art, the typical tolerance along thelength of the corresponding tapered surfaces of the shank portion of thetool holder and corresponding recess of the spindle is about ±0.040inches. In accordance with the present invention, it is contemplatedthat the tapered outer surface 15 of the shank portion 14 will be sizedand configured such that the typical tolerance along the length of theouter surface 15 of the shank portion 14 and corresponding tapered innersurface 17 of the recess 16 will be approximately ±0.015 inches.Typically, the tool holder 10 is secured to the spindle 12 by drawingthe shank portion 14 upwardly into the recess 16, as will be discussedin more detail below.

In addition to the shank portion 14, the tool holder 10 comprises acutting tool mounting portion 18. The mounting portion 18 itself definesa cylindrically configured upper section 20, and a cylindricallyconfigured lower section 22. The lower section 22 extends axially fromthe upper section 20 and has an outer diameter which is less than thatof the upper section 20 such that an annular shoulder 24 is definedbetween the upper and lower sections 20, 22. Extending axially withinthe lower section 22 of the mounting portion 18 is a central aperture 26which is adapted to receive the shank portion 28 of a cutting tool 30.Though not shown, it will be recognized that the mounting portion 18 ofthe tool holder 10 may be of uniform diameter rather than including thedifferently sized upper and lower sections 20, 22 described above.

In addition to the shank and mounting portions 14, 18, the tool holdercomprises a circularly configured flange portion 34 which is formedbetween the shank portion 14 and the upper section 20 of the mountingportion 18. The flange portion 34 extends radially outward relative tothe shank portion 14 and the upper section 20, and includes a generallyV-shaped slot 36 disposed within the peripheral edge thereof andextending circumferentially thereabout. The slot 36 is adapted toaccommodate a tool holder changer (not shown) to carry and contact thetool holder 10 for automatic removal and insertion of the tool holder 10from and into the spindle 12. Those skilled in the art will recognizethat that the tool holder 10 of the present invention bears generalsimilarity to standard tool holder dimensional configurations such asthe American Standard, Japanese B.T., European B.N., German DINStandard, and Caterpillar V-Flange Standard.

Referring now to FIGS. 2 and 3, in addition to the slot 36, the flangeportion 34 defines a generally planar top surface 38 which circumventsthe base of the shank portion 14, and an opposed, generally planarbottom surface 40 which circumvents the base of the upper section 20 ofthe mounting portion 18. Disposed in the top surface 38 of the flangeportion 34 is a continuous, annular groove or channel 42 which is of aprescribed width, depth and shape. As best seen in FIG. 4, the channel42 has a generally quadrangular (e.g., rectangular) cross-sectionalconfiguration defining a generally planar bottom wall or surface 44 anda spaced pair of concentric side walls or surfaces 46 which extendgenerally perpendicularly between the bottom surface 44 of the channel42 and the top surface 38 of the flange portion 34.

The tool holder 10 of the present invention further comprises anannular, ring-like dampening member 48 which is disposed within thechannel 42 of the flange portion 34. The dampening member 48 ispreferably fabricated from a compressible material, such as anelastomeric material. The dampening member 48 is shown in a compressedstate in FIGS. 2 and 3, and in an uncompressed state in FIGS. 4 and 5.As will be recognized by those of ordinary skill in the art, thedampening member 48 is in its uncompressed state (as shown in FIG. 4)prior to the interface of the tool holder 10 to the spindle 12. Thedampening member 48 is preferably sized relative to the channel 42 suchthat when the dampening member 48 is in its uncompressed state, a smallportion of the dampening member 48 protrudes upwardly beyond the topsurface 38 of the flange portion 34, with a small gap or space beingdefined between the dampening member 48 and each of the side surfaces 46defined by the channel 42.

As is best shown in FIGS. 2 and 3, the initial advancement of the shankportion 14 of the tool holder 10 into the recess 16 of the spindle 12 islimited by the abutment of the dampening member 48 against the annular,generally planar distal end surface 50 defined by the spindle 12. Fullysecuring the tool holder 10 to the spindle 12 by drawing the shankportion 14 upwardly into the recess 16 facilitates the compression ofthe dampening member 48 in a manner wherein the compressed dampeningmember 48 substantially fills or occupies the open area defined by thechannel 42 when the same is enclosed by the distal end surface 50 of thespindle 12. In this regard, the movement of the shank portion 14upwardly into the recess 16 is intended to be limited only by thedirect, metal-to-metal contact between the distal end surface 50 of thespindle 12 and the top surface 38 of the flange portion 34. As indicatedabove, such abutting engagement facilitates the effective enclosure ofthe channel 42 by the distal end surface 50 of the spindle 12. Since thedampening member 48 is sized such that, when compressed, itsubstantially fills the available open area defined by the enclosedchannel 42, the dampening member 48 is thus operative to impart aresilient biasing force against both the tool holder 10 and the spindle12 seated there against. When the dampening member 48 is compressed inthis manner, it is adapted to effectively dampen and thus substantiallyeliminate the harmonic resonance normally transferred into the toolholder 10 by the cutting tool 30. The dampening of such harmonicresonance prevents slight movements of the cutting tool 30 relative tothe tool holder 10 which could cause cuts made by the cutting head ofthe cutting tool 30 to be substantially out of tolerance or, in extremecases, could result in the loosening of the tool holder 10 within thespindle 12. Though direct, metal-to-metal contact between the distal endsurface 50 of the spindle 12 and the top surface 38 of the flangeportion 34 is preferred, the dampening functionality of the compresseddampening member 48 is realized even if such metal-to-metal contact isnot achieved.

In addition to dampening harmonic resonance in the aforementionedmanner, the dampening member 48, when compressed in the manner shown inFIGS. 2 and 3, creates a seal between the flange portion 34 and thedistal end surface 50 of the spindle 12. The seal created by thedampening member 48 prevents debris, cutting oil, or other contaminantsfrom getting between the outer surface 15 of the shank portion 14 andthe inner surface 17 of the recess 16, thus maintaining the cleanlinessof the combined tool holder 10 and spindle 12. The reduced contaminationeffectuated by the seal also leads to far less runout and dramaticallyimproves cutting tolerances.

Referring now to FIGS. 5 and 5A, in accordance with a relatively minorvariant of the tool holder 10 shown in FIGS. 1-4, it is contemplatedthat a continuous, annular groove 52 may optionally be formed in thebottom surface 44 of the channel 42. The groove 52 preferably has agenerally semi-spherical cross-sectional configuration, and is formed inthe bottom surface 44 of the channel 42 so as to be substantiallyequidistantly spaced concentrically between the side surfaces 46 definedby the channel 42. When the dampening member 48 is in its uncompressedstate as shown in FIG. 5, the dampening member 48 typically extendsalong and thus covers or encloses the groove 52. When the dampeningmember 48 is in its compressed state as shown in FIG. 5A, the groove 52is substantially filled thereby. Thus, the groove 52, if included in thechannel 42, provides additional area for accommodating the compresseddampening member 48.

Referring now to FIG. 6, further in accordance with the presentinvention, it is contemplated that the dampening member 48 may be sizedto have a diameter less than that of the channel 42 such that somedegree of resilient expansion or enlargement of the dampening member 48must occur to facilitate the insertion thereof into the channel 42. Asis best seen in FIG. 6, such enlargement of the dampening member 48results in the occurrence of a Poisson contraction therein whicheffectively reduces the height of the dampening member 48 to a leveljust protruding slightly beyond the top surface 38 of the flange portion34. In addition to this height reduction of the dampening member 48, thesame is maintained in biased engagement to the innermost side surface 46defined by the channel 42, thus effectively maintaining the dampeningmember 48 within the channel 42. When the dampening member 48 is putinto its compressed state by its abutment against the distal end surface50 defined by the spindle 12, the dampening member 48 shown in itsuncompressed state in FIG. 6 essentially assumes the same profile asthat shown by the dampening member 48 in FIGS. 2 and 3.

In the tool holder 10 of the present invention, the shank portion 28 ofthe cutting tool 30 is preferably secured within the central aperture 26of the lower section 22 of the mounting portion 18 via a heat shrinkingprocess. In this respect, the aperture 26 is sized to have a diameterwhich is slightly less than the diameter of the shank portion 28. Theapplication of heat to the lower section 22 via a heat source as aninduction heater effectively increases the diameter of the aperture 26,thus allowing the shank portion 28 to be slideably inserted therein to adesired axial position. When the external application of heat via theinduction heater is discontinued and the lower section 22 of themounting portion 18 allowed to cool back to ambient temperature, thermalcontraction causes the aperture 26 to form a rigid interference, i.e., ametal-to-metal fit, between the lower section 22 of the mounting portion18 and the shank portion 28 of the cutting tool 30. As such, the heatshrinking process rigidly maintains the cutting tool 30 within the toolholder 10 in a concentric fashion for high tolerance machiningapplications. The use of the heat shrinking process prevents thenon-concentric mounting of the cutting tool 30 within the tool holder 10in view of the uniform engagement between the inner surface of the lowersection 22 defining the aperture 26 and the outer surface of the shankportion 28 of the cutting tool 30.

The tool holder 10 of the present invention is preferably used byinitially inserting the shank portion 14 into the recess 16 in theaforementioned manner such that the top surface 38 of the flange portion34 is brought into direct contact with the distal end surface 50 of thespindle 12, such abutting contact resulting in the compression of thedampening member 48 as described above. Thereafter, the shank portion 28of the cutting tool 30 is heat shrunk within the lower section 22 of themounting portion 18 to facilitate the concentric attachment of thecutting tool 30 to the tool holder 10. Those of ordinary skill in theart will recognize that the cutting tool 30 may be attached to the toolholder 10 prior to the tool holder 10 being secured within the spindle12.

Referring now to FIG. 7, there is shown a tool holder 10 a constructedin accordance with a second embodiment of the present invention. Thetool holder 10 a is structurally identical to the above-described toolholder 10, with the distinction between the tool holders 10, 10 a lyingin the inclusion of additional dampening members 54 within the shankportion 14 a of the tool holder 10 a. More particularly, the tool holder10 a is preferably formed to include a plurality of continuous channelsor grooves 56 which are formed in the tapered outer surface 15 a of theshank portion 14 a in spaced, generally parallel relation to each otherand to the flange portion 34 a. Disposed within each of the grooves 56is a respective one of the dampening members 54. As will be recognizedby those of ordinary skill in the art, due to the tapered configurationof the shank portion 14 a, the circumference of the groove 56 disposedclosest to the flange portion 34 a exceeds the circumference of thegroove 56 disposed furthest from the flange portion 34 a. In thisregard, the grooves 56 are of progressively decreasing circumference asthey are disposed further from the flange portion 34 a. Importantly,each of the grooves 56 is formed to have a depth such that when acorresponding one of the dampening members 54 is completely insertedtherein, only a small portion of such dampening member 54 protrudes fromthe outer surface 15 a of the shank portion 14 a.

When the shank portion 14 a is advanced into the recess 16 of thespindle 12, the dampening members 54 are adapted to supplement thevibration or harmonic resonance dampening effect of the dampening member48 a of the tool holder 10 a. In this regard, due to the closetolerances between the outer surface 15 a of the shank portion 14 a andthe inner surface 17 defined by the recess 16 of the spindle 12 asdescribed above, the complete advancement of the shank portion 14 a intothe recess 16 (i.e. the abutment of the top surface 38 a of the flangeportion 34 a against the distal end surface 50) results in thecompression of the dampening members 54 in a manner resulting in thedirect, metal-to-metal contact between the outer surface 15 a of theshank portion 14 a and the inner surface 17 of the recess 16. In thisregard, the dampening members 54 and the grooves 56 are sized relativeto each other such that the compression of each dampening member 54causes it to substantially fills the available open area defined by thecorresponding enclosed groove 56, the compressed dampening members 54thus being operative to impart a resilient biasing force against boththe tool holder 10 a and the spindle 12 seated there against. When thedampening members 54 are compressed in this manner, they are adapted tosupplement the effect of the compressed dampening member 48 a and toeffectively dampen and thus substantially eliminate the harmonicresonance normally transferred into the tool holder 10 a by the cuttingtool 30. Though the shank portion 14 a of the tool holder 10 a is shownas including four dampening members 54 in FIG. 7, those of ordinaryskill in the art will recognize that fewer or greater than fourdampening members 54 may be included in the shank portion 14 a withoutdeparting from the spirit and scope of the present invention.Additionally, though not shown, it is contemplated that the groove(s) 56and corresponding dampening member(s) 54 may alternatively be configuredto extend generally linearly between the distal end of the shank portion14 a and the top surface 38 a of the flange portion 34 a in any one of awide variety of numbers and spatial separations. Further, though beingintended to supplement the effect of the dampening member 48 a, those ofordinary skill in the art will recognize that the dampening member(s) 54may be used independently of the dampening member 48 a, i.e., thedampening member 48 a need not necessarily be included in the toolholder 10 a.

Referring now to FIG. 8, in accordance with another aspect of thepresent invention, it is contemplated that the tapered inner surface 17partially defining the recess 16 of the spindle 12 may include aplurality of grooves 58 therein which accommodate dampening members 60.More particularly, the spindle 12 is preferably formed to include aplurality of the continuous grooves 58 which are formed in the taperedinner surface 17 of the spindle 12 in spaced, generally parallelrelation to each other. Disposed within each of the grooves 58 is arespective one of the dampening members 60. As will be recognized bythose of ordinary skill in the art, due to the tapered configuration ofthe inner surface 17, the circumference of the groove 58 disposedclosest to the distal end surface 50 exceeds the circumference of thegroove 58 disposed furthest from the distal end surface 50. In thisregard, the grooves 58 are of progressively decreasing circumference asthey are disposed further from the distal end surface 50. Importantly,each of the grooves 58 is formed to have a depth such that when acorresponding one of the dampening members 60 is completely insertedtherein, only a small portion of such dampening member 60 protrudes fromthe inner surface 17 of the spindle 12.

When the shank portion 14 of the tool holder 10 described above isadvanced into the recess 16 of the spindle 12, the dampening members 60are adapted to supplement the vibration or harmonic resonance dampeningeffect of the dampening member 48 of the tool holder 10. In this regard,due to the close tolerances between the outer surface 15 of the shankportion 14 and the inner surface 17 defined by the recess 16 of thespindle 12 as described above, the complete advancement of the shankportion 14 into the recess 16 (i.e. the abutment of the top surface 38of the flange portion 34 against the distal end surface 50) results inthe compression of the dampening members 60 in a manner resulting in thedirect, metal-to-metal contact between the outer surface 15 of the shankportion 14 and the inner surface 17 of the recess 16. In this regard,the dampening members 60 and the grooves 58 are sized relative to eachother such that the compression of each dampening member 60 causes it tosubstantially fills the available open area defined by the correspondingenclosed groove 58, the compressed dampening members 60 thus beingoperative to impart a resilient biasing force against both the toolholder 10 and the spindle 12. When the dampening members 60 arecompressed in this manner, they are adapted to supplement the effect ofthe compressed dampening member 48 of the tool holder 10 and toeffectively dampen and thus substantially eliminate the harmonicresonance normally transferred into the tool holder 10 by the cuttingtool 30. Though the inner surface 17 of the spindle 12 is shown asincluding four dampening members 60 in FIG. 8, those of ordinary skillin the art will recognize that fewer or greater than four dampeningmembers 60 may be included in the inner surface 17 without departingfrom the spirit and scope of the present invention. Additionally, thoughnot shown, it is contemplated that the groove(s) 58 and correspondingdampening member(s) 60 may alternatively be configured to extendgenerally linearly between the innermost end of the recess 16 and thedistal end surface 50 of the spindle 12 in any one of a wide variety ofnumbers and spatial separations. Further, though being intended tosupplement the effect of the dampening member 48 of the tool holder 10,those of ordinary skill in the art will recognize that the dampeningmember(s) 60 may be used independently of the dampening member 48, i.e.,the dampening member 48 need not necessarily be included in the toolholder 10.

Referring now to FIG. 9, in accordance with yet another aspect of thepresent invention, in the tool holder 10 described above, the shankportion 14 is provided with an internally threaded aperture 62 whichextends axially through at least a portion thereof. More particularly,the aperture 62 extends axially from the distal end of the shank portion14 disposed furthest from the flange portion 34, and may extend all theway to the flange portion 34 into communication with the aperture 26which extends through the mounting portion 18 as described above.Additionally, the aperture 62 may be provided with a right-handedinternal threads suitable for threadably accommodating theabove-described externally threaded bolt which is advanced through aportion of the spindle 12 and is threadably received into the aperture62, the tightening of such bolt by the rotation thereof in a clockwisedirection being used to effectively draw the shank portion 14 upwardlyinto the recess 16 of the spindle 12 until such time as the flangeportion 34 is seated against the distal end surface 50.

In the tool holder 10, it is contemplated that the aperture 62 may beinternally threaded with a left-handed thread as opposed to the moreconventional right-handed thread. Such left-handed thread of theaperture 62 would be used to accommodate a corresponding left-handedthread included on any corresponding retention member used inconjunction with the tool holder 10. Once such retention member is anextension member 64 which may threaded into the aperture 62 in themanner shown in FIG. 9, such threadable engagement being facilitated bythe rotation of the extension member 64 in a counter-clockwisedirection. More particularly, the extension member 64 comprises anexternally threaded end portion 66 which is received into the aperture62, the end portion 66 transitioning into an enlarged diameter centralportion 68. The central portion 68 of the extension member 64 itselftransitions into a retention knob portion 70. The retention knob portion70 is formed to have a bulbous configuration having a generallyfrusto-conical shaped flange 72 which is adapted to engaged a pair ofdraw bar ears or retention members 74 (depicted in phantom lines in FIG.9) of a conventional tool changer retention device disposed within theinterior of the spindle 12.

As is apparent from FIG. 9, the adaptation of the tool holder 10 for usewith an automatic tool changer system is accomplished by simplythreading the end portion 66 of the extension member 64 into thecomplimentary internally threaded aperture 62 extending within the shankportion 14 of the tool holder 10 until such time as an annular shoulder76 defined by the central portion 68 abuts the distal end of the shankportion 14. The tool holder 10 with the cutting tool 30 mounted withinthe aperture 26 may then be automatically inserted into the spindle 12by the automatic tool changer mechanism which holds the tool holder 10by interaction with the V-shaped slot 36 formed within the flangeportion 34. The tool changer then advances the shank portion 14 into therecess 16, with the tool holder retention members 74 then beingautomatically operative to move radially inward toward the retentionknob portion 70 and, upon contacting the same, to subsequently moveaxially away from the flange portion 34 to draw the tool holder 10inwardly into the recess 16 of the spindle 12 until such time as theflange portion 34 is abutted against the distal end surface 50.

Advantageously, due to the threadable engagement of the extension member64 to the tool holder 10 through the use of corresponding, complimentaryleft-handed threads, the subsequent rotation of the tool holder 10 andspindle 12 in a clockwise direction as normally occurs during theperformance of a cutting operation through the use of the cutting tool30 does not result in any loosening of the extension member 64 withinthe shank portion 14, as could result in a loss of concentricity and thegeneration of harmonic resonance. Rather, the corresponding left handedthreads actually tighten the contact between the extension member 64 andthe shank portion 14, which assists in preventing the formation of aseparation gap between the flange portion 34 and the distal end surface50. Additionally, it is contemplated that the engagement between theextension member 64 and shank portion 14 of the tool holder 10 may befurther strengthened through the use of a heat shrinking process. Inthis respect, the application of heat to the shank portion 14 may beconducted in a manner wherein the aperture 62 is enlarged to a dimensionsufficient to allow for the threadable advancement of the end portion 66of the extension member 64 thereinto. Upon the abutment of the shoulder76 against the distal end of the shank portion 14, the subsequentcooling of the shank portion 14 constricts the same about the endportion 66, thus firmly engaging the extension member 64 to the toolholder 10.

Still further in accordance with the present invention, it iscontemplated that the vibration/harmonic resonance dampening effects ofthe tool holders 10, 10 a may be enhanced by at least partiallyfabricating the same from a heavy metal material (e.g., mercury,tungsten, lead) or a combination of heavy metal materials. However, ifsuch heavy metal material(s) is/are used in relation to the fabricationof the tool holders 10, 10 a, it is further contemplated that themaximum temperature to which the tool holders 10, 10 a may be heatedthrough the use of an induction heater to facilitate the mounting of thecutting tool 30 and/or the extension member 64 thereto will bemaintained below a prescribed limit to avoid triggering any adversereactions from such heavy metal material(s).

Referring now to FIG. 10, there is shown a tool holder 10 b which isconstructed in accordance with a third embodiment of the presentinvention and is also adapted for use in the rotating spindle 12. Thetool holder 10 b comprises a cutting tool mounting portion 18 b. Themounting portion 18 b itself defines a cylindrically configured uppersection 20 b, and a cylindrically configured lower section 22 b. Thelower section 22 b extends axially from the upper section 20 b, and hasan outer diameter which is less than that of the upper section 20 b suchthat an annular shoulder 24 b is defined between the upper and lowersections 20 b, 22 b. Extending axially within the lower section 22 b isa central aperture 26 b which is adapted to receive the shank portion 28of the cutting tool 30. It will be recognized that the mounting portion18 b may be of uniform diameter rather than including the differentlysized upper and lower sections 20 b, 22 b described above and shown inFIG. 10.

The tool holder 10 b further comprises a circularly configured flangeportion 34 b which is formed at the end of the upper section 20 b of themounting portion 18 b opposite that having the lower section 22 bprotruding therefrom. The flange portion 34 b extends radially outwardrelative to the upper section 20 b, and includes a generally V-shapedslot 36 b disposed within the peripheral edge thereof and extendingcircumferentially thereabout. In addition to the slot 36 b, the flangeportion 34 b defines a generally planar top surface 38 b and an opposed,generally planar bottom surface 40 b which circumvents the base of theupper section 20 b. Disposed on the top surface 38 b is a continuous,annular groove or channel 42 b which is of a prescribed width and depth.The structural attributes of the channel 42 b are the same as thosedescribed above in relation to the channel 42 of the tool holder 10. Inthis regard, in the tool holder 10 b, the channel 42 b is used toaccommodate a dampening member (not shown in FIG. 10) like the dampeningmember 48 also shown and described above in relation to the tool holder10.

The tool holder 10 b of the third embodiment further comprises agenerally cylindrical shank portion 14 b which protrudes axially fromthe top surface 38 b of the flange portion 34 b. The shank portion 40 bis provided with an internally threaded aperture 62 b which extendsaxially through at least a portion thereof. More particularly, theaperture 62 b extends axially from the distal end of the shank portion14 b disposed furthest from the flange portion 34 b, and may extend allthe way to the flange portion 34 b into communication with the aperture26 b which extends through the mounting portion 18 b as described above.

Also included in the tool holder 10 b is a generally conical sleeve 78which is rigidly attached to the shank portion 14 b via a heat shrinkfit process, as will be described in more detail below. The sleeve 78defines an annular bottom end 80 which is of a first diameter, and anannular top end 82 which is of a second diameter less than the firstdiameter. The sleeve 78 further defines a tapered outer surface 84 whichextends between the bottom and top ends 80, 82 thereof. Additionally,extending axially through the sleeve 78 between the bottom and top ends80, 82 thereof is a bore 86 of substantially constant diameter. The bore86 is sized to have an inner diameter which is slightly less than theouter diameter of the shank portion 14 b. The application of heat to thesleeve 78 via a heat source such as an induction heater effectivelyincreases the diameter of the bore 86, thus allowing the sleeve 78 to beslideably advanced over the shank portion 14 b. The advancement of thesleeve 78 along the shank portion 14 b is limited by the abutment of thebottom end 80 of the sleeve 78 against the top surface 38 b of theflange portion 34 b. The shank portion 14 b and sleeves 78 are sizedrelative to each other such that when the bottom end 80 is abuttedagainst the top surface 38 b of the flange portion 34 b, the distal endof the shank portion 14 b is substantially flush or continuous with thetop end 82 of the sleeve 78, in the manner shown in FIG. 10. When theexternal application of heat via the induction heater is discontinuedand the sleeve 78 allowed to cool back to ambient temperature, thermalcontraction facilitates the formation of a rigid interface (i.e., ametal-to-metal fit) between the sleeve 78 and the shank portion 14 b. Aswill be recognized by those of ordinary skill in the art, thecombination of the shank portion 14 b and sleeve 78 in the tool holder10 b collectively defines a structure possessing substantially the samestructural and functional attributes of the shank portion 14 of theabove-described tool holder 10. In this regard, the slope of the taperedouter surface 84 of the sleeve 78 corresponds to the slope of thetapered inner surface 17 of the recess 16 within the spindle 12, withthe sleeve 78 being firmly seated within the recess 16 when the toolholder 10 b is properly secured to the spindle 12. Though not shown inFIG. 10, it is contemplated that all or at least a portion of the outersurface 84 of the sleeve 78 may include a coating of vulcanized rubberapplied thereto to provide extra gripping power when the sleeve 78 isadvanced into the recess 16 of the spindle 12. Such gripping power maybe enhanced by the optional inclusion of a grit mixed in with thevulcanized rubber. It is further contemplated that the outer surface 15of the shank portion 14 of the tool holder 10 described above mayinclude such vulcanized rubber coating on all or at least a portionthereof.

Though not shown, the spindle 12 may be outfitted to include a pair oftabs which are attached to the distal end surface 50 so as to beseparated from each other by a prescribed distance. These tabs aretypically secured to the spindle 12 via respective bolts which areadvanced through complimentary openings extending through the tabs andinto respective ones of a complimentary pair of internally threadedapertures disposed within the distal end surface 50 of the spindle 12.These tabs are adapted to be used in conjunction with tool holders whichinclude a corresponding pair of notches or recesses within the radiallyextending flange portion thereof. These recesses are separated from eachother at an interval of approximately 180°, and receive respective onesof the tabs once the shank portion of such tool holder is fully insertedinto the recess 16 of the spindle 12. The receipt of the tabs into therespective ones of the recesses is use to prevent any slippage of thetool holder relative to the spindle 12. As will be recognized, if thetool holder does not include such recesses in the flange portionthereof, the tabs protruding from the distal end surface 50 would not beneeded, and thus would be removed since they would otherwise interferewith the continuous flange portion. The tool holders 10, 10 a, 10 bdescribed above and constructed in accordance with the present inventioninclude continuous flange portions 34, 34 a, 34 b which are devoid ofthe aforementioned recesses.

Upon the removal of the tabs from the distal end surface 50 of thespindle 12, the internally threaded openings remain in the distal endsurface 50. In order to effectively plug these openings when the spindle12 is to be used in conjunction with any of the tool holders 10, 10 a,10 b which do not include the recesses as indicated above, such toolholders 10, 10 a, 10 b may each be optionally outfitted with the adapterring 88 shown in FIG. 11. The adapter ring 88 includes an annular mainbody 90 having a pair of cylindrical projections 92 protruding from acommon side or surface thereof. The distance separating the projections92 from each other is adapted to mirror the distance separating theapertures disposed in the distal end surface 50 of the spindle 12 whichare exposed as a result of removal of the tabs therefrom. The adapterring 88 is used by advancing the same over the shank portion 14, 14 a orsleeve 78 until such time as the side of the main body 90 opposite thathaving the projections 92 extending therefrom is abutted against thedampening member 48, 48 a. The subsequent complete advancement of theshank portion 14, 14 a or sleeve 78 into the recess 16 results in theinsertion of the projections 92 into respective ones of the apertureswithin the distal end surface 50, and the abutment of the side of themain body 90 having the projections 92 extending therefrom against thedistal end surface 50. The compression of the dampening member 48, 48 aalso results in the side of the main body 90 opposite that having theprojections 92 protruding therefrom potentially coming into direct,metal-to-metal contact with the top surface 38, 38 a, 38 b of the flangeportion 34, 34 a, 34 b.

Though not shown, those of ordinary skill in the art will recognize thatthe adapter ring 88 need not necessarily be provided with theprojections 92. In this regard, though the projections 92 effectivelyfill portions of the apertures which may be included in the distal endsurface 50, a variant of the adapter ring 88 not including theprojections 92 would still be operative to effectively cover the openapertures within the distal end surface 50 of the spindle 12.

This disclosure provides exemplary embodiments of the present invention.The scope of the present invention is not limited by these exemplaryembodiments. Numerous variations, whether explicitly provided for by thespecification or implied by the specification, such as variations instructure, dimension, type of material and manufacturing process may beimplemented by one of skill in the art in view of this disclosure.

1. A tool holder for use in a rotating spindle of a cutting machine, thetool holder comprising: a conically tapered shank portion; a cuttingtool mounting portion; a flange portion disposed between the shank andmounting portions, the flange portion defining opposed, generally planartop and bottom surfaces and including a continuous channel which isdisposed within the top surface and circumvents the shank portion; and adampening member disposed within the channel of the flange portion; thedampening member being compressible between the flange portion and thespindle when the tool holder is inserted into the spindle, and sized andconfigured to exert a biasing force against the tool holder and thespindle when compressed which is operative to dampen a harmonicresonance attributable to use of the tool holder with a cutting tool. 2.The tool holder of claim 1 wherein the dampening member is fabricatedfrom an elastomeric material.
 3. The tool holder of claim 1 wherein: thechannel defines a bottom wall and a spaced pair of concentric side wallswhich extend generally perpendicularly between the bottom wall of thechannel and the top surface of the flange portion; and the dampeningmember is sized and configured relative to the channel such that aprescribed level of clearance exists between the dampening member andthe side walls of the channel when the dampening member is in anuncompressed state.
 4. The tool holder of claim 3 wherein the channelfurther includes a continuous groove which is disposed within the bottomwall thereof, the groove being substantially covered and enclosed by thedampening member.
 5. The tool holder of claim 4 wherein the groove has agenerally semi-spherical cross-sectional configuration.
 6. The toolholder of claim 1 wherein the channel has a generally rectangularcross-sectional configuration.
 7. The tool holder of claim 1 wherein:the channel defines a bottom wall and a spaced pair of concentric sidewalls which extend generally perpendicularly between the bottom wall ofthe channel and the top surface of the flange portion; and the dampeningmember is sized and configured relative to the channel such that a thedampening member is resiliently biased against an innermost one of theside walls of the channel when the dampening member is in anuncompressed state.
 8. The tool holder of claim 1 wherein the toolholder is fabricated from a heavy metal material.
 9. The tool holder ofclaim 1 wherein: the shank portion defines a tapered outer surface; therotating spindle of the cutting machine has a recess which is at leastpartially defined by a tapered inner surface of the spindle; and theouter and inner surfaces are formed to have a tolerance along thelengths thereof of approximately +/−0.015 inches when the shank portionis fully inserted into the recess of the spindle.
 10. The tool holder ofclaim 1 wherein the shank portion includes an aperture which extendsaxially through at least a portion thereof and is internally threadedwith a left-handed thread.
 11. The tool holder of claim 10 further incombination with an extension member having an end portion with aleft-handed thread which is threadably receivable into the aperture ofthe shank portion.
 12. The tool holder of claim 1 wherein: the shankportion defines a tapered outer surface having at least one continuousgroove extending circumferentially thereabout; and a dampening member isdisposed in the groove, the dampening member being sized to protrudeslightly beyond the outer surface.
 13. The tool holder of claim 12wherein the shank portion includes a plurality of grooves disposedtherein in spaced, generally parallel relation to each other and to theflange portion, each of the grooves having a dampening member disposedtherein.
 14. In a tool holder having a conically tapered shank portionfor insertion into a rotating spindle of a cutting machine, a cuttingtool mounting portion, and a flange portion disposed between the shankand mounting portions, the improvement comprising: a dampening memberwhich is located with a complimentary channel disposed within the flangeportion and is compressible between the flange portion and the spindlewhen the tool holder is inserted thereinto, the dampening member beingadapted to eliminate harmonic resonance attributable to the use of thetool holder with a cutting tool.
 15. The tool holder of claim 14wherein: the channel defines a bottom wall and a spaced pair ofconcentric side walls which extend generally perpendicularly between thebottom wall of the channel and the top surface of the flange portion;and the dampening member is sized and configured relative to the channelsuch that a prescribed level of clearance exists between the dampeningmember and the side walls of the channel when the dampening member is inan uncompressed state.
 16. The tool holder of claim 15 wherein thechannel further includes a continuous groove which is disposed withinthe bottom wall thereof, the groove being substantially covered andenclosed by the dampening member.
 17. The tool holder of claim 16wherein the groove has a generally semi-spherical cross-sectionalconfiguration.
 18. The tool holder of claim 14 wherein the channel has agenerally rectangular cross-sectional configuration.
 19. The tool holderof claim 14 wherein: the channel defines a bottom wall and a spaced pairof concentric side walls which extend generally perpendicularly betweenthe bottom wall of the channel and the top surface of the flangeportion; and the dampening member is sized and configured relative tothe channel such that a the dampening member is resiliently biasedagainst an innermost one the side walls of the channel when thedampening member is in an uncompressed state.
 20. A tool holder for usein a rotating spindle of a cutting machine, the tool holder comprising:a shank portion; a cutting tool mounting portion; a flange portiondisposed between the shank and mounting portions, the flange portionincluding a continuous channel disposed therein; and a dampening memberdisposed within the channel of the flange portion; the dampening memberbeing compressible between the flange portion and the spindle when thetool holder is inserted into the spindle, and sized and configured todampen a harmonic resonance attributable to use of the tool holder witha cutting tool when compressed between the flange portion and thespindle.
 21. A method for securing a tool holder to a spindle, themethod comprising the steps of: providing a threaded aperture within ashank portion of the tool holder; heating the shank portion of the toolholder to enlarge the threaded aperture; threading a threaded endportion of an extension member into the heated shank portion; andcooling the shank portion.
 22. The method of claim 21 further comprisingthe steps forming the threaded aperture and the threaded end portionwith left handed threads.
 23. The method of claim 21 further comprisingthe steps of: inserting the shank portion of the tool holder into arecess of the spindle from a first side of the spindle; and pulling theextension member from an opposed second side of the spindle to completeinsertion of the shank portion of the tool holder into the recess of thespindle.